The present disclosure relates to image forming apparatuses and methods for adjusting the sensitivity of an optical sensor.
There is well known, as an example of a general image forming apparatus, an electrophotographic image forming apparatus constituted by five processes: uniformly electrically charging an uncharged photoconductor (charging process); irradiating the surface of the charged photoconductor with laser light based on an original document to be copied, thus forming a latent image of the original document on the surface of the photoconductor (exposure process); making the latent image visible with toner (development process); transferring a toner image formed by making the visible image to a recording medium, such as a paper sheet, placed on a transfer belt (transfer process), and fixing the transferred toner image on the recording medium (fixation process).
Toner on the surface of the photoconductor is not entirely transferred to the recording medium but a small amount of the toner remains on the surface of the photoconductor. The toner remaining on the surface of the photoconductor is collected as waste toner by a cleaning device and conveyed to a waster toner bottle or the like. For example, toner remaining untransferred on the surface of the photoconductor is scraped off from the surface of the photoconductor by a cleaning blade made of resin or other materials, conveyed through a waste toner conveying pipe, and finally collected into the waste toner bottle.
An image forming apparatus to which such a waste toner bottle can be attached is provided with a means for detecting that the waste toner bottle has been filled with waste toner. An example of the method for detecting that the waste toner bottle is filled with waste toner is a method in which a pair of light-emitting and light-receiving parts of an optical sensor are disposed near an inlet of the waste toner bottle with the inlet between them and the waste toner bottle is determined to be full when light emitted from the light-emitting part is blocked by the waste toner accumulated in the waste toner bottle and thus the optical sensor detects that the amount of light received by the light-receiving part has become small.
An LED constituting a component of the light-emitting part of the optical sensor and a phototransistor constituting a component of the light-receiving part thereof have a problem that their performances significantly vary among individual pieces, so that the sensitivity of the optical sensor also significantly varies from combination to combination of the pair of light-emitting and light-receiving parts. Therefore, after the optical sensor is mounted to the apparatus body, it is necessary to adjust, for each apparatus, the light intensity of the LED and the sensitivity of light falling on the phototransistor, thus adjusting the sensitivity of the optical sensor. Various methods for adjusting the sensitivity of light falling on the phototransistor are proposed.